Abstract

Five grazing experiments are described where ewes were fed forages which are likely to increase the absorption of essential amino acids (EAA) for periods of 63-70 days, immediately before and during mating, relative to control ewes mated on grass based pastures. The legume Lotus corniculatus (Birdsfoot trefoil CV Grassland Goldie) was fed in two experiments and supplements of willow or poplar forage trees were given to ewes mated on low quality drought pasture in three experiments. Both L. corniculatus and the forage trees contained condensed tannins (CT) and in addition the crude protein content of the forage trees (166 g/kg DM) was much higher than that of drought pasture (122 g/kg DM). Mating on L. corniculatus and supplementing with forage trees consistently increased lambing percentage. Lamb mortality between birth and weaning was significantly reduced (P<0.05) by mating on L. corniculatus in one experiment and by feeding forage trees during mating in one experiment. Similar trends of smaller magnitude were evident in the other experiments and did not attain statistical significance. Hypotheses of how feeding these forages during mating may have reduced post-natal lamb mortality are advanced and methods of testing the hypotheses are suggested.

TN, Barry, TJ Parkinson, CA Ramirez-Restrepo, EL McWilliam, and N Lopez-Villalobos

Proceedings of the New Zealand Society of Animal Production, Volume 64, Hamilton, 30-33, 2004